Final answer:
The medullary reticular nuclei inhibit stretch reflexes by providing inhibitory modulation to the motor neurons, which helps to regulate muscle contraction, tone, and coordination.
Step-by-step explanation:
The medullary reticular nuclei act to inhibit stretch reflexes by modulating proprioceptive feedback. This feedback inhibition is crucial in maintaining muscle tone and coordination during movement. The stretch reflex is an automatic response elicited when a muscle spindle, a stretch receptor within the muscle, is stretched. An impulse is sent to the spinal cord, which then sends back signals to the muscle, resulting in contraction. In addition to this direct response, the medullary reticular formation sends inhibitory signals to the motor neurons to moderate the contraction and prevent excessive muscle tension, thus maintaining balance and body posture.